Full-wave versus half-wave discriminating rectification apparatus for testing electrical characteristics of a diode



1966 E. R. DOUBEK, JR 3,286, 2

FULL-WAVE VERSUS HALF-WAVE DISCRIMINATING RECTIFICATION APPARATUS FORTESTING ELECTRICAL CHARACTERISTICS OF A DIODE Original Filed June 5,1962 v 201) 23 --n v INDICA'I'OR o United States Patent Ofitice3,286,182 Patented Nov. 15, 1966 FULL-WAVE VERSUS HALF-WAVE DISCRIMINAT-ING RECTIFICATION APPARATUS FOR TEST- ING ELECTRICAL CHARACTERISTICS OFA DIODE Edward R. Doubek, Jr., Brookfield, Ill., assignor to WesternElectric Company, Incorporated, New York, N.Y., a corporation of NewYork Continuation of abandoned application Ser. No. 200,175, June 5,1962. This application June 11, 1965, Ser. No. 466,511

5 Claims. (Cl. 324-158)- This invention relates generally to electricalcomponent testing devices, and more specifically to a device for testingdiodes.

This application is a continuation of copending US. application SerialNo. 200,175, filed June 5, 1962, nOW abandoned.

Large numbers of diodes are currently employed in the construction ofprinted circuit boards and other types of electronic assemblies.However, before the diodes can be incorporated into a circuit it isnecessary to perform tests for determining the forward. to reverseresistance ratio and for determining whether or not the current passingdirection of the diodes corresponds to their labelled current passingdirection.

Presently the techniques used for determining the forward and reverseresistance of diodes involves testing each diodes with an ohm-meter or acurve tracer. Using these techniques, the forward and reverse resistanceof each diode is measured separately thereby necessitating removing andreversing each diode in the ohm-meter to accomplish both measurements.Thereafter, the directional characteristics of the diode must also bechecked before the diode is incorporated in a circuit in order toestablish whether or not the diode is properly'aligned in its labelledcurrent passing direction.

Broadly, it is an object of this invention to provide a diode testingdevice wherein a diode can be tested in a single operation, the requiredminimum value for the forward to reverse resistance ratio as well as thedirectional characteristic of the diode being checked simultaneously bythe device.

More specifically, it is an object of this invention to provide a testdevice of the above character wherein the forward to reverse resistanceratioof the tested diode is automatically compared to that of areference diode, and wherein the directional characteristic of the diodeunder test is also simultaneously ascertained.

Other objects, advantages and novel aspects of the invention will becomeapparent upon reference to the following detailed description, taken inconjunction with the appended drawing, in which the diode testing deviceof this invention is shown.

According to this invention a diode tester is provided, which includes arectifying circuit adapted to receive a diode under test, thecharacteristics and directional orientation of that diode being comparedto the characteristics and orientation of a reference diode permanentlyconnected in the rectifying circuit. When the diode under test isinserted into the rectifying circuit it essentially converts therectifying circuit from a half-wave rectifier to a full-wave rectifier.A discriminator is provided which in response to full-wave rectificationof a prescribed quantity, as measured by the amplitude of a componentharmonic frequency of electrical signal representative of full-waverectification, discriminates at an amplitude indicative of a desiredforward to reverse resistance ratio of the diode under test.

In a preferred embodiment, such discriminator includes a filterconnected to the output of the rectifying circuit which filters out thefundamental harmonic frequency of the alternating current source andpasses the second harmonic when the diode under test functions properlyand is properly orientated to pass the source current. An electrondischarge device which is rendered normally nonconductive when not inoperation is rendered conductive when the voltage of the second harmonicpassed by the filter is applied to the control grid of the dischargedevice. A variable impedance is connected to the control grid and isadjustable so that only voltage signals from the filter network havingsome pre-established minimum amplitude level will cause conduction inthe discharge device. Thus if the characteristics of the diode undertest do not meet some standard as established by the reference diode andthe variable impedance, the diode under test will be unacceptable.

Referring now to the drawing for a more complete understanding of thisinvention it is seen that the diode testing device is formed by anormally half-wave rectifying circuit'referred to by the numeral 10 inwhich the diode D is permanently connected as a reference diode orstandard against which the characteristics of the diode D under test isto be compared. The diode D is properly orientated with respect to itslabelled current passing direction in the rectifying circuit 10. Therectifying circuit 10 is designed to receive the diode D betweennormally open contacts K and K so that the half-wave rectifying circuit10 is converted to a full-wave rectifying circuit upon insertion of thediode D therein in the proper current passing direction. 7

A source 11 of alternating current, of for example, 60 cycles persecond, is used to bias the diode tested and it will be understood thatdifferent frequency sources can also be used if the various componentsforming the testing device are redesigned to function at that differentfrequency.

The secondary coil 12 of a step-up transformer 13 is connected at theends thereof by the leads 14 and 14a and at the center thereof by acenter tap 15. The resistors 16a, 17a and 16b, 17b are respectivelyconnected in parallel to the transformer 13 between the leads 14 and 14aand the center tap 15. The resistors 16a and 16b allow tapping of thetransformer 13 as by the conductors 18 and 19 so as to provide a safeoperating voltage for the operator if the diode D is manually loaded inthe tester and yet provide voltage having an amplitude such that thediode D can be tested at the desired voltage level. The resistors 16aand 16b also limit the amount of current the diodes can draw so that thereference diode D will not be damaged if the diode D is shorted.

A frequency sensitive filter network 20 comprising the resistors 20a,20b and 20c and the capacitors 20d, 20a and 20 is designed to recognizethe difference in the harmonic content of an electrical signal betweenfull and half-wave rectification, and to select a component harmonicwhich in a Fourier series analysis of the signal is representative offull-wave rectification. This may be accomplished, for example, bydesigning the network 20 to filter out the fundamental frequency of thesource voltage (representative of half-wave rectification) and passvoltages rich in the second harmonic which is representative offull-wave rectification to a variable resistor 22. While aresistance-capacitance filter 20 is illustrated, other types of filterscan alternatively be used, as will be evident to those working in theart.

Since a 60 cycle per second source of current is being used, the filter20 is designed to filter out the fundamental of 60 cycles per second andpass the second harmonic of cycles per second. If the diode D is absentfrom the rectifying circuit or is open or shorted, the voltage at theterminal 23 will be rich in the fundamental which will then be filteredout by the filter 20 so that the voltage at the terminal 25 will be zeroor very close to zero, the proximity to zero being dependent upon theefficiency at which the filter 20 operates. If the diode D is reversedfrom the labelled current passing direction in the rectify ing circuitcurrent will only be passed by the diode D and this current will befiltered out so that the voltage at the terminal 25 will again be zeroor very close to zero.

A test diode D which is not open or shorted, and which has a properdirectional characteristic, generally provides full-wave rectificationand the representative second harmonic signal will pass through thefilter 20. However, the quality of the full-wave rectification dependsupon the forward to reverse resistance ratio of the test diode D; ascompared to that of the standard diode D Since the forward to reverseresistance ratio of the standard diode D is fixed as a reference level,the quality of full-wave rectification is made to depend upon theforward to reverse resistance ratio of the test diode D Thus, the filternetwork isolates the second harmonic frequency so that the quality offull-wave rectification, and more particularly the forward to reverseresistance ratio of the test diode D may be measured. When the diode Dcompares favorably with the standard diode D the voltage at the terminal23 will be rich in the second harmonic which will be passed by thefilter 20 so that the voltage at the terminal 25 will be rich in the 120cycle frequency, The amplitude of the second harmonic voltage signalpassed by the filter 20 is representative of the quality of full-waverectification, and since-such quality depends upon the forward toreverse resistance ratio of the test diode D the amplitudeof the secondharmonic signal may be monitored for a prescribed minimum valueindicative of a maximum acceptable forward to-reverse resistance ratiofor the diode under test. In the preferred embodiment, a control'grid 26of a thyratron tube 27 is brought out to a resistor 24 and to thevariable resistor a 22. Resistance values of the resistors 22 and 24 canbe varied such that a minimum voltage must be applied to the grid 26before the'thyratron will fire. Thus the resistor 22 can be adjusted toestablish a level of discrimination in the amplitude of the secondharmonic signal corresponding to the lower-limit of the forward torearward resistance ratio that the diode D must have before thethyratron tube 27 will fire. A B+ voltage source for the thyratron 27 isprovided by a rectifier tube 28 and'a resistance-capacitance filter,referred to generally by the numeral 29, comprising resistors 29a, 29b,29c and capacitors 29d and 29e. A pair of conventional'voltageregulating tubes 30 and 31 are provided in the circuit to insure stableoperation ofthe thyratron 27. A current limiting resistor 34 isconnected to the output of the thyratron 27 and to an indicator 35 whichmaybe a light, buzzer or the like,

A normally open switch 36 is manually closed after the diode D isinserted into the rectifying circuit, and if the diode D meets thestandard as established by the diode D and the variable resistor 22, andis properly orientated in the direction of its labelled current passingdirection, the thyratron tube 27 will conduct to energize the indicator35. After each test the switch 36 is manually opened again tode-energize the tube 27 in preparation for subsequent tests.

As will be apparent to those skilled in the art, the diode testingdevice of this invention can be used in combination with mechanism forinserting the diodes under test between the contacts K1 and K2, andthereafter rotating the diode 180 if the diode initially fails to passthe directional characteristic test. Further, it is obvious that bestsensitivity may be obtained where the forward to reverse resistanceratio of the standard diode equals that desired of the test diode, butother values may be used so long as they are compatible with thediscriminating criterion of a prescribed quality level of full-waverectification.

It is to be understood that the above-described arrangements are simplyillustrative of the application of the principles of this invention.Numerous other arrangements may be readily devised by those skilled inthe art which will'embody the principles of the invention and fallwithin the spirit and scope thereof.

What is claimed is:

1. A diode testing device for simultaneously comparing the forward toreverse resistance ratio of the diode under test to that of a referencediode and determining if the labelled directional characteristic of thediode under test is correctly oriented with the true current passingdirection thereof, the device comprising:

a source of alternating current;

a diode rectifying circuit connected to said source, one diode in saidcircuit being connected therein as a reference diode;

means in said circuit for receiving a test diode therein,

the insertion of the test diode in said circuit converting said circuitfrom a half-wave rectifier to a fullwave rectifier when the currentpassing direction of the test diode corresponds to the labelleddirectional characteristic thereof;

a network connected to the output of said rectifying circuit forfiltering out the fundamental harmonic of the alternating current sourceand passing higherorder harmonics produced by full-wave rectification;electron discharge device connected to the output of the network; andmeans for controlling the conduction of said electron discharge devicein response to the output of said network sovthat said discharge deviceis rendered conductive by a voltage signal of some predetermined minimumamplitude indicative of a maximum acceptable forward to reverseresistance ratio of the test diode. 2. A diode testing device forsimultaneously comparing I, the forward to reverse resistance ratio ofthe diode under test to that of a reference diode and determining if thelabelled directional characteristic of the diode under test is correctlyoriented with the true current passing direction thereof, the devicecomprising:

a source of alternating current;

a diode rectifying circuit connected to said source, one diode in saidcircuit being connected therein as a reference diode;

means in said circuit being adapted to receive a test 1diode therein,"the insertion of the test diode in said circuit converting said circuitfrom a half-wave rectifier to a full-wave rectifier when the currentpassing direction of the test diode corresponds to the labelleddirectional characteristic thereof;

a filter connected to the output of said rectifying circuit forfiltering out the fundamental harmonic of the alternating current sourceand passing higherorder harmonics produced by full-wave rectification;

an electron discharge device connected to the output of said filter;

means for normally rendering said discharge device nonconductive and forrendering said discharge device conductive in response to a voltagesignal passed by the filter having some predetermined minimum amplitudeindicative of a maximum acceptable forward to reverse resistance ratioof the test diode; and

means for indicating the presence of an acceptable test diode in saidcircuit connected to said discharge device and energized by operationthereof.

3. A diode testing device for simultaneously determining if the forwardto reverse resistance ratio of the diode under test is equal to or lessthan that of a reference diode and the labelled directionalcharacteristic of the diode under test is correctly oriented with thetrue current passing direction thereof, the device comprising:

a source of alternating current;

a diode rectifying circuit connected to said source,

one diode in said circuit being permanently connected therein as areference diode;

a pair of open contact elements in said circuit for receiving a testdiode therebetween, the insertion of the test diode in said circuitconverting said circuit from a half-wave rectifier to a full-waverectifier when the current passing direction of the test diodecorresponds to the labelled directional characteristics thereof;

means for indicating the presence of an acceptable test diode in saidcircuit;

a filter connected to the output of said rectifying circuit forfiltering out the fundamental harmonic of the alternating current sourceand passing higherorder harmonics produced by full-wave rectification;

a normally nonconductive electron discharge device connected to theoutput of said filter including at least two electrodes and a controlgrid between said electrodes for rendering said discharge deviceconductive, one electrode connected to the alternating current source,and other electrode connected to the indicating means for energizingsaid means upon operation of said discharge device; and

variable impedance means connected to the output of said filter and tosaid control grid for producing a biasing voltage on said grid, saidimpedance means being adjusted such that only a voltage signal passed bysaid filter having some predetermined minimum amplitude causes operationof said discharge device.

4. A test circuit for determining the rectification characteristics of adiode, which comprises:

a source of alternating current;

a diode rectifying circuit connected to said source, said circuitincluding a reference diode for rectifying alternate half-cycles of thecurrent;

means arranged in said rectifying circuit to receive a test diode forrectifying half-cycles of the current which are complementary to saidalternate halfcycles of the current, thereby normally converting saidrectifying circuit to a full-wave rectifier;

filter means connected to the output of said rectifying circuit for atleast partially suppressing the fundamental signal frequency and forselectively differentiating an electrical signal comprised of at leastone uninhibited higher-order component harmonic frequency representativeof full-wave rectification; and

2,522,369 3,064,190 11/1962 Inderweisen 324128 X resistance ratio of adiode under test to that of a reference diode, which comprises:

a source of alternating current;

a diode rectifying circuit connected to said source and including areference diode for rectifying alternate half-cycles of the current;

means for arranging a test diode in said rectifying circuit to form afull-wave rectifier, said test diode rectifying half-cycles of currentwhich are complementary to said alternate half-cycles;

a network connected to said rectifying circuit for filtering out thefundamental harmonic in the output signal thereof and for passinghigher-order harmonics produced by full-wave rectification;

means responsive to the output signal of said network, fordiscriminating at a predetermined amplitude of the higher-order harmonicfrequencies indicative of full-wave rectification, said predeterminedamplitude corresponding to a maximum acceptable forward to reverseresistance ratio of the test diode; and

means responsive to the discriminating means for indicating whether thetest diode possesses the desired forward to reverse resistance ratio.

References Cited by the Examiner UNITED STATES PATENTS 9/1950 Guanella324-128 X OTHER REFERENCES Electronics (Ives), March 1, 1957, pp.194-195. Vacuum Tube Circuits and Transistors (Arguimbau),

WALTER L. CARLSON, Primary Examiner.

E. L. STOLARUN, Assistant Examiner.

4. A TEST CIRCUIT FOR DETERMINING THE RECTIFICATION CHARACTERISTICS OF ADIODE, WHICH COMPRISES: A SOURCE OF ALTERNATING CURRENT; A DIODERECTIFYING CIRCUIT CONNECTED TO SAID SOURCE, SAID CIRCUIT INCLUDING AREFERENCE DIODE FOR RECTIFYING ALTERNATE HALF-CYCLES OF THE CURRENT;MEANS ARRANGED IN SAID RECTIFYING CIRCUIT TO RECEIVE A TEST DIODE FORRECTIFYNG HALF-CYCLES ON THE CURRENT WHICH ARE COMPLEMENTARY TO SAIDALTERNATE HALFCYCLES OF THE CURRENT, THEREBY NORMALLY CONVERTING SAIDRECTIFYING CIRCUIT TO A FULL-WAVE RECTIFIER; FILTER MEANS CONNECTED TOTHE OUTPUT OF SAID RECTIFYING CIRCUIT FOR AT LEAST PARTIALLY SUPPRESSINGTHE FUNDAMENTAL SIGNAL FREQUENCY AND FOR SELECTIVELY DIFFERENTIATING ANELECTRICAL SIGNAL COMPRISED OF AT LEAST ONE UNINHIBITED HIGHER-OVERCOMPONENT HARMONIC FREQUENCY RESPRESENTATIVE OF FULL-WAVE RECTIFICATION;AND MEANS RESPONSIVE TO THE ELECTRICAL OUTPUT SIGNAL OF SAID FILTERMEANS FOR DISCRIMINATING AT A PREDETERMINED AMPLITUDE THE HIGHER-ORDERCOMPONENT FREQUENCY REPRESENTATIVE OF FULL-WAVE RECTIFICATION, THEATTAINMENT BY SAID OUTPUT SIGNAL OF SAID PREDETERMINED AMPLITUDE BEINGINDICATIVE OF A MINIMUM ACCEPTABLE QUALITY OF RECIFICATION EFFECTED BYTHE TEST DIODE.